Aspis has the following salient features: (i) Under weak attacks where the Byzantines act independently (without significant collusion) they will always be detected by the proposed novel clique-based algorithm. (ii) Furthermore, Aspis is resilient to stronger attacks where adversaries collude in optimal ways; these are much stronger than those considered in prior work. In particular, instead of simulating a random set of adversaries [1]}, [2]}, we have crafted a non-trivial attack specifically designed for our system such that the adversaries can evade detection and potentially corrupt more gradient values.
